Gaia Data Release 2 Hambly, N. C.; Cropper, M.; Boudreault, S. ...
Astronomy & astrophysics,
08/2018, Volume:
616
Journal Article
Peer reviewed
Open access
Context. The European Space Agency’s Gaia satellite was launched into orbit around L2 in December 2013. This ambitious mission has strict requirements on residual systematic errors resulting from ...instrumental corrections in order to meet a design goal of sub-10 microarcsecond astrometry. During the design and build phase of the science instruments, various critical calibrations were studied in detail to ensure that this goal could be met in orbit. In particular, it was determined that the video-chain offsets on the analogue side of the analogue-to-digital conversion electronics exhibited instabilities that could not be mitigated fully by modifications to the flight hardware. Aims. We provide a detailed description of the behaviour of the electronic offset levels on short (<1 ms) timescales, identifying various systematic effects that are known collectively as “offset non-uniformities”. The effects manifest themselves as transient perturbations on the gross zero-point electronic offset level that is routinely monitored as part of the overall calibration process. Methods. Using in-orbit special calibration sequences along with simple parametric models, we show how the effects can be calibrated, and how these calibrations are applied to the science data. While the calibration part of the process is relatively straightforward, the application of the calibrations during science data processing requires a detailed on-ground reconstruction of the readout timing of each charge-coupled device (CCD) sample on each device in order to predict correctly the highly time-dependent nature of the corrections. Results. We demonstrate the effectiveness of our offset non-uniformity models in mitigating the effects in Gaia data. Conclusions. We demonstrate for all CCDs and operating instrument/modes on board Gaia that the video-chain noise-limited performance is recovered in the vast majority of science samples.
The Spanish Central Pyrenees have been the scenario of at least two damaging earthquakes in the last 800 years. Analysis of macroseismic data of the most recent one, the Vielha earthquake (19 ...November 1923), has led to the identification of the North Maladeta Fault (NMF) as the seismic source of the event. This E–W trending fault defines the northern boundary of the Maladeta Batholith and corresponds to a segment of the Alpine Gavarnie thrust fault. Our study shows that the NMF offsets a reference Neogene peneplain. The maximum observed vertical displacement is ∼
730 m, with the northern downthrown sector slightly tilting towards the South. This offset provides evidence of normal faulting and together with the presence of tectonic faceted spurs allowed us to geomorphically identify a fault trace of 17.5 km. This length suggests that a maximum earthquake of
M
w
=
6.5
±
0.66 could occur in the area. The geomorphological study was improved with a resistivity model obtained at Prüedo, where a unique detritic Late Miocene sequence crops out adjacent to the NMF. The section is made up of 13 audiomagnetotelluric soundings along a 1.5 km transect perpendicular to the fault trace at Prüedo and reveals the structure in depth, allowing us to interpret the Late Miocene deposits as tectonically trapped basin deposits associated with normal faulting of the NMF. The indirect age of these deposits has been constrained between 11.1 and 8.7 Ma, which represents a minimum age for the elevated Pyrenean peneplain in this part of the Pyrenees. Therefore, we propose the maximum vertical dip-slip rate for the NMF to be between 0.06 and 0.08 mm/a. Normal faulting in this area is attributed to the vertical lithospheric stress associated with the thickened Pyrenean crust.
Gaia Data Release 3 Arenou, F.; Lammers, U. L.; Mignard, F. ...
Astronomy and astrophysics (Berlin),
06/2023, Volume:
674, Issue:
A1
Journal Article, Web Resource
Peer reviewed
Open access
Context.
We present the third data release of the European Space Agency’s
Gaia
mission,
Gaia
DR3. This release includes a large variety of new data products, notably a much expanded radial velocity ...survey and a very extensive astrophysical characterisation of
Gaia
sources.
Aims.
We outline the content and the properties of
Gaia
DR3, providing an overview of the main improvements in the data processing in comparison with previous data releases (where applicable) and a brief discussion of the limitations of the data in this release.
Methods.
The
Gaia
DR3 catalogue is the outcome of the processing of raw data collected with the
Gaia
instruments during the first 34 months of the mission by the
Gaia
Data Processing and Analysis Consortium.
Results.
The
Gaia
DR3 catalogue contains the same source list, celestial positions, proper motions, parallaxes, and broad band photometry in the
G
,
G
BP
, and
G
RP
pass-bands already present in the Early Third Data Release,
Gaia
EDR3.
Gaia
DR3 introduces an impressive wealth of new data products. More than 33 million objects in the ranges
G
RVS
< 14 and 3100 <
T
eff
< 14 500, have new determinations of their mean radial velocities based on data collected by
Gaia
. We provide
G
RVS
magnitudes for most sources with radial velocities, and a line broadening parameter is listed for a subset of these. Mean
Gaia
spectra are made available to the community. The
Gaia
DR3 catalogue includes about 1 million mean spectra from the radial velocity spectrometer, and about 220 million low-resolution blue and red prism photometer BP/RP mean spectra. The results of the analysis of epoch photometry are provided for some 10 million sources across 24 variability types.
Gaia
DR3 includes astrophysical parameters and source class probabilities for about 470 million and 1500 million sources, respectively, including stars, galaxies, and quasars. Orbital elements and trend parameters are provided for some 800 000 astrometric, spectroscopic and eclipsing binaries. More than 150 000 Solar System objects, including new discoveries, with preliminary orbital solutions and individual epoch observations are part of this release. Reflectance spectra derived from the epoch BP/RP spectral data are published for about 60 000 asteroids. Finally, an additional data set is provided, namely the
Gaia
Andromeda Photometric Survey, consisting of the photometric time series for all sources located in a 5.5 degree radius field centred on the Andromeda galaxy.
Conclusions.
This data release represents a major advance with respect to
Gaia
DR2 and
Gaia
EDR3 because of the unprecedented quantity, quality, and variety of source astrophysical data. To date this is the largest collection of all-sky spectrophotometry, radial velocities, variables, and astrophysical parameters derived from both low- and high-resolution spectra and includes a spectrophotometric and dynamical survey of SSOs of the highest accuracy. The non-single star content surpasses the existing data by orders of magnitude. The quasar host and galaxy light profile collection is the first such survey that is all sky and space based. The astrophysical information provided in
Gaia
DR3 will unleash the full potential of
Gaia
’s exquisite astrometric, photometric, and radial velocity surveys.
Gaia Early Data Release 3 Brown, A. G. A.; Prusti, T.; Eyer, L. ...
Astronomy and astrophysics (Berlin),
05/2021, Volume:
649
Journal Article, Web Resource
Peer reviewed
Open access
Context.
We present the early installment of the third
Gaia
data release,
Gaia
EDR3, consisting of astrometry and photometry for 1.8 billion sources brighter than magnitude 21, complemented with the ...list of radial velocities from
Gaia
DR2.
Aims.
A summary of the contents of
Gaia
EDR3 is presented, accompanied by a discussion on the differences with respect to
Gaia
DR2 and an overview of the main limitations which are present in the survey. Recommendations are made on the responsible use of
Gaia
EDR3 results.
Methods.
The raw data collected with the
Gaia
instruments during the first 34 months of the mission have been processed by the
Gaia
Data Processing and Analysis Consortium and turned into this early third data release, which represents a major advance with respect to
Gaia
DR2 in terms of astrometric and photometric precision, accuracy, and homogeneity.
Results. Gaia
EDR3 contains celestial positions and the apparent brightness in
G
for approximately 1.8 billion sources. For 1.5 billion of those sources, parallaxes, proper motions, and the (
G
BP
−
G
RP
) colour are also available. The passbands for
G
,
G
BP
, and
G
RP
are provided as part of the release. For ease of use, the 7 million radial velocities from
Gaia
DR2 are included in this release, after the removal of a small number of spurious values. New radial velocities will appear as part of
Gaia
DR3. Finally,
Gaia
EDR3 represents an updated materialisation of the celestial reference frame (CRF) in the optical, the
Gaia
-CRF3, which is based solely on extragalactic sources. The creation of the source list for
Gaia
EDR3 includes enhancements that make it more robust with respect to high proper motion stars, and the disturbing effects of spurious and partially resolved sources. The source list is largely the same as that for
Gaia
DR2, but it does feature new sources and there are some notable changes. The source list will not change for
Gaia
DR3.
Conclusions. Gaia
EDR3 represents a significant advance over
Gaia
DR2, with parallax precisions increased by 30 per cent, proper motion precisions increased by a factor of 2, and the systematic errors in the astrometry suppressed by 30–40% for the parallaxes and by a factor ~2.5 for the proper motions. The photometry also features increased precision, but above all much better homogeneity across colour, magnitude, and celestial position. A single passband for
G
,
G
BP
, and
G
RP
is valid over the entire magnitude and colour range, with no systematics above the 1% level
Summary of the contents and survey properties Brown, A.G.A.; Granvik, Mikael; Zwitter, T.
Astronomy and astrophysics (Berlin),
2018, 2018-01-01, Volume:
16, Issue:
A1
Journal Article
Peer reviewed
Open access
Context. We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on astrophysical parameters and variability, for sources brighter ...than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. Aims. A summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. Methods. The raw data collected with the Gaia instruments during the first 22 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to Gaia DR1 in terms of completeness, performance, and richness of the data products. Results. Gaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0 : 5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the G(BP) (330-680 nm) and G(RP) (630-1050 nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14 000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent. Conclusions. Gaia DR2 represents a major achievement for the Gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the Gaia survey which covers a very substantial fraction of the volume of our galaxy.
In this work we present a study of an alluvial fan system, which is affected by the Quaternary activity of the leftlateral, reverse Alhama de Murcia Fault (Betic Cordillera). Paleoseismic studies in ...this area yield data that can be compared and correlated with the morphologic and tectono-sedimentary evolution of the alluvial fan. The spatial arrangement of the sedimentary alluvial fan units near the fault zone, shown in trenches, is controlled by the recurrent reverse, left-lateral coseismic events. We analysed the morphology of the drainage network using a 1:5000 scale orthoimage to identify and measure horizontal deflections along the fault. The channel pattern analysis allowed us to estimate the average horizontal slip rate of the SAMF for the last 130 ka. This value is 0.21 mm/a, which is slightly higher than the range of values obtained by trenching analysis for the last 30 ka, (0.06 to 0.15 mm/yr). The interpretation of the stratigraphic sequence exposed along the trench walls constrained the occurrence of at least two surface faulting earthquakes during the last 30000 years. The most recent event happened after the El Saltador Creek dissected the alluvial fan. The penultimate event occurred while the alluvial fan was still active.
The Gaia mission Vallenari, A.; Bailer-Jones, C. A. L.; Milligan, D. J. ...
Astronomy and astrophysics (Berlin),
11/2016, Volume:
595
Journal Article, Web Resource
Peer reviewed
Open access
Gaia is a cornerstone mission in the science programme of the EuropeanSpace Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric ...concept was changed to a direct-imaging approach. Both the spacecraft and the payload were built by European industry. The involvement of the scientific community focusses on data processing for which the international Gaia Data Processing and Analysis Consortium (DPAC) was selected in 2007. Gaia was launched on 19 December 2013 and arrived at its operating point, the second Lagrange point of the Sun-Earth-Moon system, a few weeks later. The commissioning of the spacecraft and payload was completed on 19 July 2014. The nominal five-year mission started with four weeks of special, ecliptic-pole scanning and subsequently transferred into full-sky scanning mode. We recall the scientific goals of Gaia and give a description of the as-built spacecraft that is currently (mid-2016) being operated to achieve these goals. We pay special attention to the payload module, the performance of which is closely related to the scientific performance of the mission. We provide a summary of the commissioning activities and findings, followed by a description of the routine operational mode. We summarise scientific performance estimates on the basis of in-orbit operations. Several intermediate Gaia data releases are planned and the data can be retrieved from the Gaia Archive, which is available through the Gaia home page.
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